Bug#827395: firefox hidden connections

[Trek]

the connections you found can be blocked by changing these
configuration directives:

browser.newtabpage.enabled
security.OCSP.enabled
browser.safebrowsing.enabled
browser.safebrowsing.malware.enabled
privacy.trackingprotection.pbmode.enabled
browser.search.suggest.enabled
browser.search.update
extensions.blocklist.enabled
extensions.update.enabled
extensions.getAddons.cache.enabled
datareporting.healthreport.service.enabled
toolkit.telemetry.enabled
network.http.speculative-parallel-limit

and may be:

beacon.enabled
browser.send_pings


from time to time I have collected a list of configuration directives
to stop automatic connections to remote hosts

you can find at http://www.trek.eu.org/text/firefox-tuning.html

I hope this can help